patch 8.2.1616: Vim9: cannot pass "true" to synID()

Problem:    Vim9: cannot pass "true" to synID().
Solution:   Use tv_get_bool_chk(). (closes #6860)
diff --git a/src/evalfunc.c b/src/evalfunc.c
index e74a82a..ea633c7 100644
--- a/src/evalfunc.c
+++ b/src/evalfunc.c
@@ -8487,7 +8487,7 @@
 
     lnum = tv_get_lnum(argvars);		// -1 on type error
     col = (linenr_T)tv_get_number(&argvars[1]) - 1;	// -1 on type error
-    trans = (int)tv_get_number_chk(&argvars[2], &transerr);
+    trans = (int)tv_get_bool_chk(&argvars[2], &transerr);
 
     if (!transerr && lnum >= 1 && lnum <= curbuf->b_ml.ml_line_count
 	    && col >= 0 && col < (long)STRLEN(ml_get(lnum)))